This disclosure relates to analysis of nuclear magnetic resonance (NMR) relaxation distributions obtained from well logging to derive information about pore size in subterranean formations.
Nuclear magnetic resonance (NMR) logging is a type of logging (e.g., wireline logging, logging while drilling (LWD) and measurement while drilling (MWD)) that uses the NMR response of a formation to directly determine its porosity and permeability, providing a continuous record along the length of the borehole
NMR logging exploits the large magnetic moment of hydrogen, which is abundant in rocks in the form of water. The NMR signal amplitude is proportional to the quantity of hydrogen nuclei present in a formation and can be calibrated to give a value for porosity. Moreover, the rate of decay of a NMR signal can be used to obtain information about the permeability of the formation.